/*
 * Copyright (C) 2010 The Android Open Source Project
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package com.example.android.apis.view;

import com.example.android.apis.R;

import android.app.Activity;
import android.app.AlertDialog;
import android.os.Bundle;
import android.view.Gravity;
import android.view.MotionEvent;
import android.view.View;
import android.view.View.OnClickListener;
import android.view.View.OnTouchListener;
import android.widget.Button;
import android.widget.Toast;

/**
 * This activity demonstrates two different ways in which views can be made more
 * secure to touch spoofing attacks by leveraging framework features.
 * 
 * The activity presents 3 buttons that obtensibly perform a risky security
 * critical function. Under ordinary circumstances, the user would never click
 * on these buttons or would at least think long and hard about it. However, a
 * carefully crafted toast can overlay the contents of the activity in such a
 * way as to make the user believe the buttons are innocuous. Since the toast
 * cannot receive input, the touches are passed down to the activity potentially
 * yielding an effect other than what the user intended.
 * 
 * To simulate the spoofing risk, this activity pops up a specially crafted
 * overlay as a toast layed out so as to cover the buttons and part of the
 * descriptive text. For the purposes of this demonstration, pretend that the
 * overlay was actually popped up by a malicious application published by the
 * International Cabal of Evil Penguins.
 * 
 * The 3 buttons are set up as follows:
 * 
 * 1. The "unsecured button" does not apply any touch filtering of any kind.
 * When the toast appears, this button remains clickable as usual which creates
 * an opportunity for spoofing to occur.
 * 
 * 2. The "built-in secured button" leverages the
 * android:filterTouchesWhenObscured view attribute to ask the framework to
 * filter out touches when the window is obscured. When the toast appears, the
 * button does not receive the touch and appears to be inoperable.
 * 
 * 3. The "custom secured button" adds a touch listener to the button which
 * intercepts the touch event and checks whether the window is obscured. If so,
 * it warns the user and drops the touch event. This example is intended to
 * demonstrate how a view can perform its own filtering and provide additional
 * feedback by examining the {@MotionEvent} flags to determine
 * whether the window is obscured. Here we use a touch listener but a custom
 * view subclass could perform the filtering by overriding
 * {@link View#onFilterTouchEventForSecurity(MotionEvent)}.
 * 
 * Refer to the comments on {@View} for more information about view
 * security.
 */
public class SecureView extends Activity {
	private int mClickCount;

	@Override
	protected void onCreate(Bundle savedInstanceState) {
		super.onCreate(savedInstanceState);

		setContentView(R.layout.secure_view);

		Button toastButton = (Button) findViewById(R.id.secure_view_toast_button);
		toastButton.setOnClickListener(new OnClickListener() {
			public void onClick(View v) {
				showOverlay();
			}
		});

		Button unsecureButton = (Button) findViewById(R.id.secure_view_unsecure_button);
		setClickedAction(unsecureButton);

		Button builtinSecureButton = (Button) findViewById(R.id.secure_view_builtin_secure_button);
		setClickedAction(builtinSecureButton);

		Button customSecureButton = (Button) findViewById(R.id.secure_view_custom_secure_button);
		setClickedAction(customSecureButton);
		setTouchFilter(customSecureButton);
	}

	private void showOverlay() {
		// Generate a toast view with a special layout that will position itself
		// right
		// on top of this view's interesting widgets. Sneaky huh?
		SecureViewOverlay overlay = (SecureViewOverlay) getLayoutInflater()
				.inflate(R.layout.secure_view_overlay, null);
		overlay.setActivityToSpoof(this);

		Toast toast = new Toast(getApplicationContext());
		toast.setGravity(Gravity.FILL, 0, 0);
		toast.setView(overlay);
		toast.show();
	}

	private void setClickedAction(Button button) {
		button.setOnClickListener(new OnClickListener() {
			public void onClick(View v) {
				String[] messages = getResources().getStringArray(
						R.array.secure_view_clicked);
				String message = messages[mClickCount++ % messages.length];

				new AlertDialog.Builder(SecureView.this)
						.setTitle(R.string.secure_view_action_dialog_title)
						.setMessage(message)
						.setNeutralButton(
								getResources()
										.getString(
												R.string.secure_view_action_dialog_dismiss),
								null).show();
			}
		});
	}

	private void setTouchFilter(Button button) {
		button.setOnTouchListener(new OnTouchListener() {
			public boolean onTouch(View v, MotionEvent event) {
				if ((event.getFlags() & MotionEvent.FLAG_WINDOW_IS_OBSCURED) != 0) {
					if (event.getAction() == MotionEvent.ACTION_UP) {
						new AlertDialog.Builder(SecureView.this)
								.setTitle(
										R.string.secure_view_caught_dialog_title)
								.setMessage(
										R.string.secure_view_caught_dialog_message)
								.setNeutralButton(
										getResources()
												.getString(
														R.string.secure_view_caught_dialog_dismiss),
										null).show();
					}
					// Return true to prevent the button from processing the
					// touch.
					return true;
				}
				return false;
			}
		});
	}
}
